Winter Storm - February 20th-21st, 2013

National Weather Service, Springfield, MO

Event Summary

A strong storm system affected much of the central U.S. including the Missouri Ozarks and extreme southeast Kansas from the evening hours on February 20th through much of the day on February 21st. Blizzard conditions affected parts of the Plains in Kansas into northwest Missouri, while across the Missouri Ozarks and southeast Kansas, a wide variety of winter weather occurred. Much of the area began with some light snow and changed over to a mix of sleet and freezing rain as warmer air moved in above the surface. Elevated instability led to numerous embedded thunderstorms which produced heavier rounds of sleet and freezing rain across the area. Across the Missouri Ozarks and southeast Kansas, 1-2 inches of a sleet and snow mix were common along with a quarter to half inch of ice. Further north across portions of west central and Central Missouri, snow was more common and 3 to 5 inches of snow occurred there.

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Event Synopsis

A strong dynamic storm system affected the Missouri Ozarks into southeast Kansas mainly during the overnight hours and through the day on February 21st, 2013. This storm system brought a wide variety of winter weather including thunder, freezing rain, sleet and snow to the region.

Dry and cold antecedent conditions led to a later onset of precipitation in the Ozarks which began as snowfall.

From the 6 pm sounding above, you can see the very dry air (green is the dew point, red is the temperature) in the lower levels that had to moisten up before precipitation would reach the ground. The initial precipitation falling was evaporating in this dry layer but also cooling the air in this column via a process called evaporative cooling.

By the midnight sounding (above), you can see the mid levels of the atmosphere had moistened up quite a bit but it was still pretty dry (although moistening) in the lower levels.

There is a lot going on here in the final 6 am sounding shown above. First of all, notice that the low levels continued to moisten overnight. Warmer air above the surface was advected in from the strong south to southwest winds with temperatures up to 4 degrees Celsius (39 deg F) within the warm nose. The helped to melt the snow as it was falling from above and then fall back to the below freezing temperatures at the surface for freezing rain. There was also enough elevated instability above the warm nose of air to promote thunderstorm development within the precipitation. Sleet became heavy at times during the bouts of thunder during the day.

Eventually during the afternoon, drier air in the mid and upper levels of the atmosphere worked into the area from the southwest and helped push the bulk of the precipitation to the east. Some moisture wrapping around the low brought some freezing drizzle to the area during the evening into parts of the overnight hours of the 22nd.

Event Radar

Below is a radar composite loop from the Springfield radar each hour from Midnight through 9 pm on Feb 21st 2013.

Event Maps

This product is an objective analysis of NWS Cooperative Observer Program (COOP) and Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) snowfall reports. CoCoRaHS data is from non-NWS sources and may have not been fully quality controlled.

Event Reports

THE TOTALS BELOW ARE SEPARATED INTO SNOW...AND ICE AND SLEETCATEGORIES...THEN BY AMOUNT...AND ARE NOT NECESSARILY THEFINAL AMOUNT FOR EACH LOCATION.